I'm an graphic artist who downloads lots and lots of preview JPEGs from commercial photograph websites. I also have a large photo collection of my own. One of my problems was that not all JPEGs have an icon that shows a picture of the file. So when I've downloaded dozens of pictures, it's sometimes hard to know which is which.

I found using Spotlight is the easy answer.

I put all my JPEGs into a folder, open the folder, and in the Spotlight search panel type jpg, and search that folder only. Presto -- up pop the JPEG icons of all my downloads as little pictures, so I can either rename or remember which is which. And of course, the same applies to other similar graphic or Photoshop files.

[robg adds: There are many third-party apps that can add image previews, saving the Spotlight step. Off the top of my head, GraphicConverter comes to mind.]

Yeah, this is how I navigate my folders-o-images. Works great for navigating through my folder of more than a thousand sketchbook scans.

if I really have a desire for preview icons I have the QuickImage control menu module but honestly, I never use it for that now that I clued in to "icon view + show icon preview". I use its multiple-file-rename capability a lot more.

Something to consider, however, is that there is a reason many JPEGs are missing previews & icons. That is: since JPEGs are most often used for images to be displayed online, previews and icons are intentionally excised to tighten up the file size, optimizing them for fastest possible download.

Best move is to make copies of these JPEG files and—if you must—add the previews and icons to the copies instead, leaving the originals untouched.

Why? Because every time you re-save a JPEG you lose image data. If your goal is just to be able to identify them with a preview (say, in folder view), do it on copies, and leave the originals intact unless you need to edit them. And if you need to edit them more than once, convert them to PSD files.